Conventionally, a temperature of a heat generating device such as a central processing unit (CPU) mounted on a motherboard is monitored by a control unit and the number of rotation of a device-specific fan or a cooling fan which cools an entire system is controlled so that the temperature of the device is adjusted at a target temperature in a personal computer and the like.
FIG. 8A is a perspective view of an example of a configuration of a conventional personal computer and FIG. 8B is a block diagram of the configuration of the personal computer illustrated in FIG. 8A. As illustrated in FIGS. 8A and 8B, a CPU-specific heatsink to which a fan is attached is adhered to a CPU which is a heat generating part mounted on a system board in this personal computer. In the fan-attached heatsink, a temperature sensor dedicated to the CPU is provided. Besides, a cooling fan for discharging, while taking in air in an outside of the housing, air in an inside of the housing is provided in a housing of the personal computer.
Then, a temperature monitor/fan controller selects a most suitable cooling measure to make a noise level appropriate by causing the temperature sensor to detect the temperature of the CPU and controlling the number of rotation of the fan-attached heatsink and the number of rotation of the cooling fan so that the temperature of the CPU is equal to or less than the target temperature. Specifically, the temperature monitor/fan controller increases the number of rotation of the fan-attached heatsink and the number of rotation of the cooling fan when the temperature of the CPU goes up and decreases the number of rotation of the fan-attached heatsink and the number of rotation of the cooling fan when the temperature of the CPU goes down as illustrated in FIG. 8C. By this, the temperature of the CPU is controlled to be within a set range for the target temperature. In this manner, the personal computer is configured to directly control and cool the CPU which is a heat generating parts by the fan-attached heatsink.
In contrast, a server installation as an information processing apparatus in which a lot of heat generating parts are mounted on a circuit board in high density is not provided with a fan-attached heatsink directly on a heat generating parts but usually configured to perform a cooling depending on a cooling fan provided in a housing.
FIG. 9A is a perspective view illustrating an example of a configuration of a conventional server installation and FIG. 9B is a block diagram of the configuration of the server installation illustrated in FIG. 9A. As illustrated in FIGS. 9A and 9B, the server installation is provided with two cooling fans in parallel for avoiding an operation stop due to a failure of a cooling fan. These cooling fans are provided at positions fronting onto an outside of the installation to make an exchange of the cooling fans easy.
In the server installation, however, the fan-attached heatsink adopted in a personal computer is not adopted. This is because the adhesion of the fan-attached heatsink to each of the numerous heat generating parts mounted on the circuit board in high density is not practical from a standpoint of space, control, and electric power consumption.
Therefore, the number of rotation of a cooling fan is controlled depending on a temperature of air taken in the inside of the housing in the server installation. For example, the number of rotation of the cooling fan is controlled to be “LOW SPEED” when the temperature of intake air is less than L1 [° C.] as illustrated in FIG. 9C. When the temperature of the intake is equal to or more than the L1 [° C.] and is less than L2 [° C.], the number of rotation of the cooling fan is controlled to be “MIDDLE SPEED”. When the temperature of the intake air is equal to or more than the L2 [° C.] and is less than L3 [° C.], the number of rotation of the cooling fan is controlled to be “HIGH SPEED”. Besides, when the temperature of the intake air becomes more than control range degree C., the installation itself is stopped to avoid a runaway effect of the server installation. More detailed information can be obtained in Japanese Laid-open Patent Publication No. 2001-42952, Japanese Laid-open Patent Publication No. 2007-60835, and Japanese Patent No. 4157550.
However, since the number of rotation of the cooling fan is controlled depending only on the temperature of the intake air into the housing in the conventional server installation as described above, the number of rotation of the cooling fan is constant at any time when the temperature of the intake air does not change. Therefore, the number of rotation of the cooling fan needs to be set on the assumption of a situation of each heat generating part operating at its maximum so that a temperature of each heat generating part will not exceed a limit value, thereby inevitably resulting in an excessive cooling as the matter stands now.
The excessive cooling performed on the assumption of the maximum operation despite no increase in temperature of each heat generating part in this manner causes problems of an increase in an electric power consumption and a noise both associated with the rotation of the cooling fan.
Because of the problems described above, there has been a challenge in how to realize an electric power saving and a noise reduction in cooling heat generating parts in a server installation. Here, the challenge lies not only in an information processing apparatus such as a server installation but also similarly in various types of electronic apparatuses which cool a plurality of heat generating parts by using a cooling device.